Expression and Functional Analysis of CYP 2 D 6 . 24 , CYP 2 D 6 . 26 , CYP 2 D 6 . 27 and CYP 2 D 7

The objectives of this study were to compare the drug-metabolizing activity of human CYP2D6.24 (I297L), CYP2D6.26 (I369T), CYP2D6.27 (E410K) allelic isoforms with wild-type CYP2D6.1, and to express the CYP2D7 protein derived from an indel polymorphism (CYP2D7 138delT) and investigate its possible codeine O-demethylase activity. Successful creation of individual cDNAs corresponding to CYP2D6*24 (2853 A>C), CYP2D6*26 (3277 T>C), CYP2D6*27 (3853 G>A) allelic variants and CYP2D7 was achieved via molecular cloning. The corresponding proteins, CYP2D6.24, CYP2D6.26, CYP2D6.27 and CYP2D7, were expressed in insect cells using a baculovirus-mediated expression system. All CYP2D proteins showed the empirical carbon monoxide difference spectra. Surprisingly, CYP2D7 protein was detected mainly in mitochondrial fraction, whereas all CYP2D6 allelic isoforms were present in microsomal fraction. Furthermore, CYP2D7 did not produce any morphine from codeine. In contrast, CYP2D6.24, CYP2D6.26 and CYP2D6.27 allelic isoforms all showed active drug-metabolizing activities towards both codeine and dextromethorphan O-demethylation. While CYP2D6.24 exhibited the highest intrinsic clearance in dextromethorphan O-demethylation (~6-fold higher than that by CYP2D6.1), it had the lowest enzyme efficiency in codeine O-demethylation (~50% lower than that by CYP2D6.1). Overall, the enzymatic consequences of CYP2D6 allelic isozymes are substrate dependent. These data would help preclinical and clinical assessment of the metabolic elimination of drugs that are mediated by human CYP2D enzyme. This article has not been copyedited and formatted. The final version may differ from this version.